Sensorless Permanent Magnet Motor Control via Phase Current Estimation
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Solution Overview
Problem
Conventional electric motor systems for auxiliary transmission pumps require resolver sensors and additional circuitry to sense rotor position and velocity, which increase costs and wiring complexity, and are problematic when submerged in transmission fluid.
Innovation Solution
A sensorless control method and system for permanent magnet synchronous motors that determines position and speed signals in a torque-speed plane using phase currents, eliminating the need for resolver sensors and reducing wiring, with a controller and sensorless position and speed estimator generating modulated control signals for the motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resolver sensors and signal digitizing circuitry are used to sense rotor position and velocity, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the rotor position and velocity sensing function from physical sensors and circuitry, and implements it through software-based estimation algorithms that calculate these parameters from readily available phase current measurements, eliminating the need for resolver sensors and their associated digitizing circuitry
Solution Approach 2:
The patent makes the phase current measurements serve multiple functions: they are used for both motor control and for estimating rotor position and velocity, eliminating the need for separate sensing circuits and reducing overall system complexity
2Measurement precision
If resolver sensors and associated circuitry are installed on the motor, then measurement precision is improved, but ease of manufacture worsens due to additional wiring
Solution Approach 1:
The patent removes the physical sensing components and their wiring from the motor assembly, replacing them with a software-based estimation system that uses existing phase current connections, thereby simplifying manufacturing and reducing wiring complexity
3Temperature
If the motor is submerged in transmission fluid for cooling and lubrication, then temperature control is improved, but reliability worsens due to problematic sensor operation in fluid
Solution Approach 1:
The patent extracts the sensing function from physical components that would be exposed to the transmission fluid, and implements it through software algorithms that process electrical signals, thereby eliminating the reliability problems associated with sensor operation in harsh fluid environments
Solution Approach 2:
The patent uses phase current measurements as an intermediary to indirectly determine rotor position and velocity without requiring direct physical sensors in the fluid environment, allowing the motor to remain submerged for cooling while maintaining reliable position sensing
Data Source
AI summary
Methods and apparatus are provided for sensorless control of a permanent magnet motor. The method includes the step of determining a sensorless position signal and a sensorless speed signal in a torque-speed plane in response to phase currents corresponding to currents on one or more of the plurality of phases.